BK2425 is a GFSK transceiver operating in the world wide ISM frequency band at 2400- 2483.5 MHz. Burst mode transmission and up to 2Mbps air data rate make them suitable for applications requiring ultra low power consumption. The embedded packet processing engines enable their full operation with a very simple MCU as a radio system. Auto re-transmission and auto acknowledge give reliable link without any MCU interference. BK2425 operates in TDD mode， either as a transmitter or as a receiver. The RF channel frequency determines the center of the channel used by BK2425. The frequency is set by the RF_CH register in register bank 0 according to the following formula： F0= 2400 + RF_CH （MHz）。 The resolution of the RF channel frequency is 1MHz. A transmitter and a receiver must be programmed with the same RF channel frequency to be able to communicate with each other. The output power of BK2425 is set by the RF_PWR bits in the RF_SETUP register. Demodulation is done with embedded data slicer and bit recovery logic. The air data rate can be programmed to 250Kbps， 1Mbps or 2Mbps by RF_DR_HIGH and RF_DR_LOW register. A transmitter and a receiver must be programmed with the same setting. In the following chapters， all registers are in register bank 0 except with explicit claim.